'\" te
.\" Copyright 1989 AT&T  Copyright (c) 2003, Sun Microsystems, Inc.  All Rights Reserved.
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.TH UNGETC 3C "Sep 10, 2003"
.SH NAME
ungetc \- push byte back into input stream
.SH SYNOPSIS
.LP
.nf
#include <stdio.h>

\fBint\fR \fBungetc\fR(\fBint\fR \fIc\fR, \fBFILE *\fR\fIstream\fR);
.fi

.SH DESCRIPTION
.sp
.LP
The \fBungetc()\fR function pushes the byte specified by \fIc\fR (converted to
an \fBunsigned char\fR) back onto the input stream pointed to by \fIstream\fR.
The pushed-back bytes will be returned by subsequent reads on that stream in
the reverse order of their pushing. A successful intervening call (with the
stream pointed to by \fIstream\fR) to a file-positioning function (
\fBfseek\fR(3C), \fBfsetpos\fR(3C) or \fBrewind\fR(3C)) discards any
pushed-back bytes for the stream. The external storage corresponding to the
stream is unchanged.
.sp
.LP
Four bytes of push-back are guaranteed.  If \fBungetc()\fR is called too many
times on the same stream without an intervening read or file-positioning
operation on that stream, the operation may fail.
.sp
.LP
If the value of \fIc\fR equals that of the macro \fBEOF\fR, the operation fails
and the input stream is unchanged.
.sp
.LP
A successful call to \fBungetc()\fR clears the end-of-file indicator for the
stream. The value of the file-position indicator for the stream after reading
or discarding all pushed-back bytes will be the same as it was before the bytes
were pushed back. The file-position indicator is decremented by each successful
call to \fBungetc()\fR; if its value was 0 before a call, its value is
indeterminate after the call.
.SH RETURN VALUES
.sp
.LP
Upon successful completion, \fBungetc()\fR returns the byte pushed back after
conversion.  Otherwise it returns \fBEOF.\fR
.SH ERRORS
.sp
.LP
No errors are defined.
.SH ATTRIBUTES
.sp
.LP
See \fBattributes\fR(7) for descriptions of the following attributes:
.sp

.sp
.TS
box;
c | c
l | l .
ATTRIBUTE TYPE	ATTRIBUTE VALUE
_
Interface Stability	Standard
_
MT-Level	MT-Safe
.TE

.SH SEE ALSO
.sp
.LP
.BR read (2),
.BR Intro (3),
.BR __fsetlocking (3C),
.BR fseek (3C),
.BR fsetpos (3C),
.BR getc (3C),
.BR setbuf (3C),
.BR stdio (3C),
.BR attributes (7),
.BR standards (7)
